Analog Integrated Circuit Device Data

22

Freescale Semiconductor

33981

TYPICAL APPLICATIONS

INTRODUCTION

TYPICAL APPLICATIONS

INTRODUCTION

Figure 20 shows a typical application for the 33981. A brush DC motor is connected to the output. A low side gate driver is

used for the freewheeling phase. Typical values for external capacitors and resistors are given.

.

Figure 20. 33981 Typical Application Diagram

EMC AND EMI RECOMMENDATIONS

INTRODUCTION

This section relates the EMC capability for 33981, High

Frequency High-current High Side Switch. This device is a

self-protected silicon switch used to replace

electromechanical relays, fuses, and discrete circuits in

power management applications.

This section presents the key features of the device and its

targeted applications. The automotive standard to measure

conducted and radiated emissions is provided. Concrete

measurements on the 33981 and improvements to reduce

electromagnetic emission are described.

DEVICE FEATURES

This 33981 is a 4.0 m

Ω self-protected, high side switch

digitally controlled from a microcontroller (MCU) with

extended diagnostics, able to drive DC motors up to 60 kHz.

A bootstrap architecture has been used to provide fast

transient gate voltage in order to reach 4.0 m

maximum at room temperature. In parallel, a charge pump is

implemented to offer continuous on-state capability. This

dual current supply of the high side MOSFET allows a duty

cycle from 5% to 100%. An external capacitor connected

between pins SR and GND is used to control the slew rate at

the output and, therefore, reduce electromagnetic

perturbations.

In standard configuration, the motor current recirculation is

handled by an external freewheeling diode. To reduce global

power dissipation, the freewheeling diode can be replaced by

an external discrete MOSFET in low side configuration. The

IC integrates a gate driver that controls and protects this

external MOSFET in the event of short-circuit to battery. The

product manages the cross conduction between the internal

high side and the external low side when used in a half-bridge

configuration. The two MOSFETs can be controlled

independently when the CONF pin is at 0V. To eliminates

fuses, the device is self-protected from severe short-circuits

(100A typical) with an innovative over-current strategy.

The 33981 has a current feedback for real-time monitoring

of the load current through an MCU analog/digital converter

to facilitate closed-loop operation for motor speed control.

The 33981 has an analog thermal feedback that can be

used by the MCU to monitor PC board temperature to

optimize the motor control and to protect the entire electronic

system. Therefore, an over-temperature shutdown feature

protects the IC against high overload condition.

MCU

33981

OUT

SR

EN

FS

INHS

CSNS

I/O

I/O

I/O

A/D

GND

VPWR

CBOOT

GLS

INLS

I/O

DLS

TEMP

A/D

CONF

OCLS

M

2.2 nF

1.0 k

Ω

1.0 k

Ω

33 k

Ω

330

μF

100 nF

100 nF

10 k

Ω

10 k

Ω

10 k

Ω

10 k

Ω

Voltage regulator